Spark gaps can operate as switches to control the flow of very large electrical currents under high voltage conditions. Typical applications include accelerators, radars, and pulsed laser systems. Spark gaps operate to prevent the flow of electrical current in high voltage applications by filling the space between a pair of electrodes with an insulating gas. When current flow is desired, a trigger pulse on an intermediate electrode or some other means is used to change the state of the insulating gas and thus create a more conductive path. The lower resistance locally leads to a rapid breakdown of the gas between the electrodes, which very rapidly produces a very low resistance conduction path or spark channel through the insulating gas, transferring electrical energy and change from source to load, and releasing high energy in various forms. Besides the light energy produced by the spark, significant amounts of thermal energy are also deposited in the gas. In addition, the rapid temperature change of the gas in the spark gap results in a series of shock and expansion waves that move outwardly from the spark gap.
Before the spark gap has recovered and can hold the high voltage of another high-energy pulse, the gas between the spark and electrodes must be returned to approximately its initial state or replaced with fresh gas. One way of rapidly increasing the resistance of the gas in the spark channel is to introduce a purge gas flow in a flow channel which sweeps the hot residue produced by preceding sparks downstream and introduces a new charge of the gas into the spark channel. While such methods are effective, it can require a great deal of energy and mechanical hardware to circulate the purge gas flow at high pulse repetition frequencies.
It is therefore desirable to have a flow channel and a spark gap switch that can operate at higher power levels and pulse repetition frequencies without requiring an externally supplied purge gas.